只获取对象的对象的一些键

Question

我有这个对象：const dataset = {  "2019": {    "a": 1,    "b": 2,    "c": 3,    "d": 4  },  "2020": {    "a": 2,    "b": 4,    "c": 6,    "d": 8  },  "2021": {    "a": 10,    "b": 11,    "c": 12,    "d": 13  }}我想获得这两个对象：const obj1 = {  "2019": {    "a": 1,    "c": 3,  },  "2020": {    "a": 2,    "c": 6,  },  "2021": {    "a": 10,    "c": 12,  }}const obj2 = {  "2019": {    "b": 2,    "d": 4  },  "2020": {    "b": 4,    "d": 8  },  "2021": {    "b": 11,    "d": 13  }}因此，根据内部对象的一些键将对象“拆分”为两个对象。这是我尝试过的：function pickKeys(dataObj, keys) {  return Object.entries(dataObj).map(([d, obj]) => {  return { [d]: _.pick(obj, keys) }})}const obj1 = pickKeys(dataset, ['a', 'c'])结果是：const obj1 = [  { '2019': { a: 1, c: 3 } },  { '2020': { a: 2, c: 6 } },  { '2021': { a: 10, c: 12 } }]所以几乎在那里，但它并不完美。哪种方法更好？

Answer 1

您可以使用map、reduce方法和一个循环的组合来执行此for...in操作，该循环会将键数组转换为对象数组。然后你可以使用数组解构来获得两个独立的对象。

const dataset = {"2019":{"a":1,"b":2,"c":3,"d":4},"2020":{"a":2,"b":4,"c":6,"d":8},"2021":{"a":10,"b":11,"c":12,"d":13}}

const [a, b] = [['a', 'c'], ['b', 'd']]

.map(keys => keys.reduce((r, key) => {

  for (let year in dataset) {

    if (!r[year]) r[year] = {}

    r[year][key] = dataset[year][key]

  }

  return r;

}, {}))

console.log(a)

console.log(b)

Answer 2

问题是map返回一个包含替换元素的数组，而你想要一个对象。

由于您已经在使用 Lodash，因此您可以使用它mapValues来转换对象的值并返回对象而不是数组。

function pickKeys(dataObj, keys) {
  return _.mapValues(dataObj, obj => _.pick(obj, keys));
}

function pickKeys(dataObj, keys) {

  return _.mapValues(dataObj, obj => _.pick(obj, keys));

}

const dataset = {

  "2019": {

    "a": 1,

    "b": 2,

    "c": 3,

    "d": 4

  },

  "2020": {

    "a": 2,

    "b": 4,

    "c": 6,

    "d": 8

  },

  "2021": {

    "a": 10,

    "b": 11,

    "c": 12,

    "d": 13

  }

}

console.log(pickKeys(dataset, ["a", "c"]));

<script src="https://cdn.jsdelivr.net/npm/lodash@4.17.15/lodash.min.js"></script>

Answer 3

下一个提供的示例代码是reduce基于、通用但在其用法中可配置的……

function createAndCollectSubdata(collector, dataEntry) {

  const { keyLists, subdataList } = collector;

  const [ dataKey, dataValue ] = dataEntry;

  keyLists.forEach((keyList, idx) => {

    const data = subdataList[idx] || (subdataList[idx] = {});

    const subdata = data[dataKey] || (data[dataKey] = {}) ;

    keyList.forEach(key => subdata[key] = dataValue[key]);

  });

  return collector;

}

const dataset = {

  "2019": {

    "a": 1,

    "b": 2,

    "c": 3,

    "d": 4

  },

  "2020": {

    "a": 2,

    "b": 4,

    "c": 6,

    "d": 8

  },

  "2021": {

    "a": 10,

    "b": 11,

    "c": 12,

    "d": 13

  }

};

const [

  acSubdata,

  bdSubdata

  

] = Object.entries(dataset).reduce(createAndCollectSubdata, {

  keyLists: [["a", "c"], ["b", "d"]],

  subdataList: []

}).subdataList;

console.log('acSubdata :', acSubdata);

console.log('bdSubdata :', bdSubdata);

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Answer 4

您可以使用给定对象的条目来映射所需的键。

const

    dataset = { 2019: { a: 1, b: 2, c: 3, d: 4 }, 2020: { a: 2, b: 4, c: 6, d: 8 }, 2021: { a: 10, b: 11, c: 12, d: 13 } },

    groups = [['a', 'c'], ['b', 'd']],

    [result1, result2] = Object

        .entries(dataset)

        .reduce((r, [k, o]) =>

            groups.map((group, i) =>

                group.reduce(

                    (q, g) => ({ ...q, [k]: { ...q[k], [g]: o[g] } }),

                    r[i] || {}

                )

            ),

            []

        );

console.log(result1);

console.log(result2);

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